Modbus-Rtu Method - Omron 3G3RX User Manual

ModBus-RTU Method

Follow the procedures below in regards to communication between the external controller and the
Inverter.
External controller
Inverter
(1) : Frame to be sent from the external control device to the Inverter (Query)
(2) : Frame to be returned from the Inverter to the external controller (Response)
(3) : Unless the Inverter completes reception of a query from the host within the time set in C077
after the Inverter completes a response (response transmission), the Inverter becomes ready
to receive the first data again. In this case, the Inverter sends no response.
Also, the Inverter's operation conforms to the setting of communication error selection C076.
For details, refer to the following table.
The receiving timeout monitor starts after the first transmission/reception is performed after
power-on or reset. Receiving timeout is inactive until reception or transmission is performed.
Parameter No. Function name
Communication error
C076
selection
Communication error
C077
timeout
C078 Communication wait time
Response from the Inverter (Frame 2) is output as return after the Inverter receives the query
(Frame 1), not output independently.
(1)
Wait time (silent interval + C078)
00: Trip
(Trip after receiving timeout [E41])
01: Decel-Trip
(Deceleration stop after receiving
timeout. Trip after stop [E41])
02: Ignore
(No trip and no alarm output)
03: Free-RUN
(Free-run stop after receiving timeout. No
trip and no alarm output)
04: Decel-Stop
(Deceleration stop after receiving
timeout. No trip and no alarm output)
0.00 to 99.99:
Time before receiving timeout
0 to 1000: Wait time until response starts after
reception is completed (excluding silent
interval)
4-4 Communication Function
(2)
(3) Communication error timeout C077
(Operates according to
communication error selection
C076 when reception times out.)
Data Default setting
(1)
Time
Unit

02

0.00

0
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